Field of the Invention
The present invention relates to an image processing method for improving a quality of a captured image.
Description of the Related Art
In image capturing through an image pickup apparatus such as a camera, part of light incident on an optical system may be reflected by a surface of a lens and a member holding the lens and arrive at an imaging plane as unnecessary light. This unnecessary light appears as an unnecessary component such as a ghost and a flare in a captured image. When a diffractive optical element is used in a telephoto lens to correct longitudinal (axial) chromatic aberration and chromatic aberration of magnification, light from a high intensity object such as the sun outside an angle of view for the image capturing may be incident on the diffractive optical element, generating unnecessary light as an unnecessary component over the entire image. Previously, a method of removing the unnecessary component by using digital image processing is known.
Japanese Patent Laid-open No. 2008-54206 discloses a method of detecting any ghost based on a difference image indicating a difference between an image (in-focus image) when an optical system is in focus on an object and an image (defocus image) when the image pickup optical system is out of focus. However, the method disclosed in Japanese Patent Laid-open No. 2008-54206 requires image capturing to be performed a plurality of times and thus is not suitable for still image pickup and moving image pickup of a moving object.
Japanese Patent Laid-open No. 2011-205531 discloses a method of detecting a ghost based on comparison of a plurality of parallax images captured by a single-lens stereoscopic image pickup. The method disclosed in Japanese Patent Laid-open No. 2011-205531, which obtains a plurality of parallax images by single image capturing, is applicable to still image pickup and moving image capturing of a moving object.
However, in the method disclosed in Japanese Patent Laid-open No. 2011-205531, an optical path for the ghost is displaced from an ideal pupil-divided optical path, and accordingly the ghost cannot be effectively reduced if the same ghost appears in both a main pixel and a subpixel while a luminance distribution is different.